cvs has an alias "ad" for the "add" subcommand. This fits nicely with
the other two-letter aliases such as "ci", "co", "di", and "up", all of
which work in svn. I've gotten used to typing "cvs ad <filename>" and
miss this in svn. It's unlikely to be mistyped, an obvious
abbreviation, and doesn't conflict with any existing svn subcommand or
alias.

As far as I can tell, the only necessary change is one line to
subversion/svn/main.c (attached).